1. Field of the Invention
The present invention is related to an apparatus and process for regulating the rate that liquid flows through an intravenous (I.V.) set used to infuse liquids and drugs into humans and animals. More particularly, the present invention is directed to an I.V. liquid flow regulator that uses a wick and a vertical tube clamp to regulate the rate of flow.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. Sections 1.97-1.99
Regulating the rate of flow through an I.V. set into a patient to achieve a desired or necessary rate of infusion of liquid or dissolved drugs is sometimes critical to successful patient treatment. Conventional I.V. sets alone do not regulate the rate of flow of liquid through them and into the patient. In these, after an initial air purge and set up, the operator adjusts the tube clamp to give the desire liquid flow setting. The conventional tube clamp is in effect a simple variable orifice device that roughly regulates the flow of liquid by squeezing the tube more or less tightly. Therefore, changes in either the upstream or downstream hydraulic conditions (as gauged from the tube clamp) will cause changes in the flow rate across the orifice. The upstream fluid head will gradually change as the fluid height in the I.V. bag or container slowly decreases. Because of the size of the container, however, and the relatively low flow rate, the change of flow rate due to the change of column height in the I.V. bag or container is slow and predictable. The change in flow rate below the tube clamp, however, has the largest unpredictable effect on the flow rate. Patient movement, such as rolling over, lifting an arm, standing, walking, sitting up and the like can cause significant changes in the patient's blood pressure, which substantially changes the rate at which the liquid will be infused into him. Further, by moving, the patient can clamp, or unclamp the vein that the catheter enters, changing the back pressure on the liquid in the I.V. set. Any movement, or even change in certain patient physiology, effectively alters the back pressure into which the catheter discharges. Additional, movement of the patient can cause the tube running to the catheter to be pinched or unpinched, changing the local flow restriction of the transport tube and the local pressure of liquid upstream of the catheter.
Changing any of these downstream conditions ultimately changes the pressure drop across the tube clamp of a common I.V. set, thus changing the flow rate from the desired settings.
Currently a number of different infusion pumps designed to provide a certain defined rate of flow and therefore infusion through an I.V. set are in use. The majority of these pumps use a roller pump designed to work against the plastic tubing of the I.V. set. Although these devices work well, they are quite expensive and can serve only one patient at a time.
Therefore, a demand exists for an I.V. liquid flow regulator that is simple, reliable, easy to manufacture and relatively inexpensive to the ultimate consumer.